Interaction of an atom with an inhomogeneous plane wave

Anatolii V Andreev, Alexander B. Kozlov

The theory of the interaction of a centrosymmetric atom with a superstrong spatially inhomogeneous laser field is developed. This theory employs the two-level approximation to describe the dynamics of spatially nonlocal interactions related to variations in the populations of the levels. We propose a model that includes spatially nonlocal interactions, such as magnetic-dipole and quadrupole interactions and interactions due to the gradient of the ponderomotive potential of the field. We consider the interaction of a homogeneous medium of centrosymmetric atoms with a superstrong laser field, which is represented as a superposition of two plane-wave ultrashort pulses propagating at some angle with respect to each other. Perturbation theory, which is valid for the fields of moderate intensity, is developed for the atomic response. The results of numerical simulations are compared with the predictions of this perturbation theory. The specific features of the nonlinear-optical response of an atom in a superstrong field are investigated. The angular distribution of the second- and third-harmonic emission is calculated in the constant-field approximation for different polarisations of the incident field.

Igor I Sobel'man

M. G. Benedict, A. M. Ermolaev, В. А. Малышев +2 more

The field acting on the atoms in a medium is different from the averaged macroscopic field. The problem of the effective local field caused by dipole–dipole interaction has been discussed several times since Lorentz. In describing the nonlinear optical properties of optically thin resonant layers, it is of principal importance to take into consideration the dipole–dipole interaction of the atoms. These effects manifest themselves when certain relations between the parameters of the atomic system and the incident field are fulfilled. The presence of the excitonic lines shows that the dipole–dipole interaction is larger than the homogeneous and inhomogeneous broadenings. This gives reason to hope that the required inequalities are satisfied in such systems. The chapter considers boundary value problem and a linearly polarized plane wave, with amplitude slowly varying during one optical period, falls perpendicularly onto the surface of a plane-parallel, optically thin, resonant layer consisting of two-level atoms.

Boris P. Antonyuk

Muhammet Ali Can, Er S. Shumovsky

We discuss the spatial properties of quantum radiation emitted by a multipole transition in a single atom. The qualitative difference between the representations of plane and spherical waves of photons is examined. In particular, the spatial inhomogeneity of the zero-point oscillations of multipole field is shown. We show that the vacuum noise of polarization is concentrated in a certain vicinity of atoms where it strongly exceeds the level predicted by the representation of the plane waves. A new general polarization matrix is proposed. It is shown that the polarization and its vacuum noise strongly depend on the distance from the source. 1 I.